The present invention relates to thermal control of power electronics, and more particularly, to the contour surface cooling of housings for power electronics devices.
The aerospace industry has many applications for power electronics devices. This is particularly true in the area of more electric architecture (MEA) for aircraft and military ground vehicles. Important applications for power electronics in the commercial aircraft business include non-bleed air environmental control systems (ECS's), variable-frequency (VF) power distribution systems, and electrical actuation. Current examples include the Boeing 787 and the Airbus Jumbo A380. The next-generation Boeing airplane (replacement of the 737), and the Airbus airplane (replacement of the A320 and A350), will most likely use MEA.
Some military aircraft already utilize MEA, including primary and secondary flight control. Military ground vehicles have migrated toward hybrid electric technology where the main propulsion is electric drives. Therefore substantial demand for electric power utilization has arisen.
Resulting from these tendencies is a significant increase in power conversion needs:                Non-bleed ECS's need additional electric drives for vapor cycle system (VCS) compressors, condenser fans, and liquid pumps.        A large number of electric drives for fans is required. In constant-frequency applications, these fans have predominantly used direct drive (no power electronics) to an induction machine. In the new environment, a double power electronics conversion AC to DC and DC to AC is required.        Auxilliary power unit (APU) and main engine electric start imposes a need for high-power, multiple-use controllers.        Military aircraft require multiple high-voltage (270-Vdc) power conversions.        Future combat systems (FCS) have generally moved toward a high-voltage power distribution system where high-power bidirectional propulsion is being used. The power generation is achieved by a main engine shaft driving a large electric machine(s); again, bidirectional conversion is required for power conditioning and self-starting.        
In this environment, there is a need for improved power converters and motor controllers for aircraft and ground military businesses for a number of reasons including, but not limited to:                Increased power-level conversion capabilities to handle increased loads;        Reduced controller weights to be able to accommodate large content increase per platform;        Reduced volume to accommodate electronics housings in limited compartment space;        Increased reliability;        Reduced cost.        
The power range for power conversion and motor control units varies from hundreds of watts to hundreds of kilowatts. The efficiency of these converters varies from 80 to 97 percent. Therefore, heat dissipation from 3 to 20 percent of the total power is required. For power conversion levels above several kilowatts, forced cooling is typically needed to achieve acceptable power density levels. The forced cooling is either air or liquid. The proper utilization of the coolant flow is achieved by using special devices called cold plates both for liquids and for air.
Cold plates with a double-sided population of components and brazed fins are very popular in the industry because they provide greater utilization of surfaces. The adhesive or brazing process forms a sandwich-like construction in which fins are permanently attached to two inner planes of the two flat metal side pieces. This structure provides containment for the air or liquid flow. The outer surfaces of the side pieces are available for installing heat-dissipating components. In some cases, the cold plate can be used as a structural carrier for heavy components.
Many high heat-dissipating devices, such as high-power switch modules (HPSM) have a flat surface for interfacing with the heat exchanger. However, some highly dissipating devices such as inductors, transformers and capacitors do not have a flat heat dissipating surface and may have a surface that is rather complex. Consequently, devices without a flat dissipating surface present special challenges in providing heat transfer to a heat exchanger. For example, devices with complex dissipating surfaces may require additional interface components and complex mounting provision to transfer heat to the heat exchanger. Also, a large number of parts, machining, and manual operations may be required. In such designs, material utilization may not be optimal. In some cases there is only line contact between component and base with large gaps for most of the external surface. The result is a heavy and expensive design with poor heat transfer effect.
As can be seen, there is a need for improved ways to cool power-dissipating power electronics components that have a non-flat, heat-dissipating external surface. There is also a need for an improved method and process to install power devices with improved thermal transfer leading to better performance and reduced cost.